1. Field of the Invention
The present invention generally relates to occupant protection devices, and particularly relates to an occupant protection device in which an airbag is stored in a center pad of a steering wheel.
2. Description of the Related Art
There is known an occupant protection device in which an airbag is stored in a folded state in a center pad of a steering wheel and the airbag expands from the center pad toward an occupant in response to an impact due to a collision of a vehicle so as to protect the occupant from the impact.
The center pad of the steering wheel usually rotates together with the steering wheel in accordance with driving operations performed by an occupant. Therefore, the airbag stored in the center pad is formed in a circular shape so as to be expandable in the same shape at any steering angle of the steering wheel. The airbag having a circular shape mainly protects the head of the occupant.
In recent years, there has been an increasing demand for an airbag that is stored in a steering wheel and is capable of not only protecting the head of an occupant but also sufficiently protecting other parts of the body. In particular, if a seat belt lies across the chest of an occupant, the seat belt might compress the chest of the occupant upon a vehicle being subjected to an impact.
In view of the foregoing, for example, Japanese Unexamined Patent Application Publication (JP-A) No. 2006-069384 discloses, as an airbag device capable of protecting not only the head of an occupant but also other parts of the body, an airbag device for an automobile in which an airbag is disposed in a center pad having a non-rotating structure and includes a head protection portion, a chest protection portion, and an abdomen protection portion.
According to JP-A No. 2006-069184, there may be a case in which an occupant is protected from an impact due to a collision of a vehicle by a portion in the vicinity of a periphery of the airbag, and there may be another case in which an occupant is protected by a portion in the vicinity of a center of the airbag, for example. More specifically, if the collision of the vehicle that has caused the impact is a front collision, it is highly likely that the occupant will be protected by the portion in the vicinity of the center of the airbag.
On the other hand, if the collision of the vehicle that has caused the impact is a side collision, it is highly likely that the occupant will be protected by the portion in the vicinity of the periphery of the airbag. Therefore, in the case where the occupant is protected by the portion in the vicinity of the center of the airbag, the impact value of the impact caused by the collision of the vehicle can be reduced. However, in the case where the occupant is protected by the portion in the vicinity of the periphery of the airbag, it may be difficult to reduce the impact value.
As can be appreciated, in the case of the airbag device of JP-A No. 2006-069384, the impact value of an impact exerted on an occupant may vary depending on the manner of the collision. That is, in the case of the airbag device of JP-A No. 2006-069384, although the airbag sufficiently protects the chest and abdomen of an occupant as described above, the occupant is not always protected by the portion in the vicinity of the center of the airbag. Thus the airbag still has room for improvement with regard to enhancing safety.